How to have person in video mask added geometry as they walk in front
In the video clip editor you can create masks and animate them with keyframes. For precise rotoscoping over video, load the video element on the Video Clip editor, create a new mask and you can animate the shape and feathering as you like.
Overlaying an image to cover a face in a video?
You can also use trackers and parent the points of the mask with the trackers, to ease the rotoscoping process.
Can a mask stick to a shape in the motion tracker?
Then you can use those masks in the compositor with a mask node that uses those masks to combine other images.
You don't need to use AfterFX.
How to draw a Rotoshape (mask) in the Compositor?
To work with geometry you can check this link as well:
Use masks as part of materials in cycles